class Solution {
public:
    bool searchMatrix(vector<vector<int>>& matrix, int target) {
        int m = matrix.size(), n = matrix[0].size();
        int x = 0, y = n - 1;
        while(x<m&&y>=0){
          if(matrix[x][y]<target){
            x++;
          }else if(matrix[x][y]>target){
            y--;
          }else{
            return true;
          }
        }
        return false;
    }
};
